class Compiler {
  constructor(vm) {
    this.el = vm.$el;
    this.vm = vm;
    this.compile(this.el);
  }

  compile(el) {
    let childNodes = el.childNodes;
    Array.from(childNodes).forEach(node => {
      if (this.isTextNode(node)) {
        this.compileText(node);
      } else if (this.isElementNode(node)) {
        this.compileElement(node);
      }

      if (node.childNodes && node.childNodes.length) {
        this.compile(node);
      }
    });
  }

  compileElement(node) {
    Array.from(node.attributes).forEach(attr => {
      let attrName = attr.name;
      if (this.isListener(attrName)) {
        let eventName = attrName.substr(5);
        let fn = this.vm.methods[attr.value];
        node.addEventListener(eventName, fn.bind(this.vm));
      } else if (this.isDirective(attrName)) {
        attrName = attrName.substr(2);
        let key = attr.value;
        this.update(node, key, attrName);
      }
    })
  }

  update(node, key, attrName) {
    let updateFn = this[attrName + 'Updater'];
    updateFn && updateFn.call(this, node, this.vm[key], key);
  }
  textUpdater(node, value, key) {
    node.textContent = value;
    new Watcher(this.vm, key, (newValue) => {
      node.textContent = newValue;
    });
  }
  modelUpdater(node, value, key) {
    node.value = value;
    new Watcher(this.vm, key, (newValue) => {
      node.value = newValue;
    });

    node.addEventListener('input', () => {
      this.vm[key] = node.value;
    });
  }
  htmlUpdater(node, value, key) {
    node.innerHTML = value;
    new Watcher(this.vm, key, (newValue) => {
      node.innerHTML = newValue;
    });
  }

  compileText(node) {
    let reg = /\{\{(.+?)\}\}/;
    let value = node.textContent;
    if (reg.test(value)) {
      let key = RegExp.$1.trim();
      node.textContent = value.replace(reg, this.vm[key]);

      new Watcher(this.vm, key, (newValue) => {
        node.textContent = newValue;
      });
    }
  }

  isDirective(attrName) {
    return attrName.startsWith('v-');
  }
  isListener(attrName) {
    return attrName.startsWith('v-on');
  }

  isTextNode(node) {
    return node.nodeType === 3;
  }

  isElementNode(node) {
    return node.nodeType === 1;
  }
}
// export default Compiler;
